As users' requirements on the wireless access rate are becoming higher and higher, WLAN which is able to provide a higher wireless access rate of data in a relatively small area has emerged as the times require. WLAN involves various kinds of techniques, the most extensively used technical standard of which is IEEE 802.11b, which uses the frequency band of 2.4 GHz and the data transmission rate of which is up to 11 Mbps. Other technical standards using the same frequency band include IEEE 802.11g and Bluetooth, wherein, the data transmission rate of IEEE 802.11g is up to 54 Mbps. Other new standards of WLAN, such as IEEE 802.11a and ETSI BRAN Hiperlan2, use the frequency band of 5 GHz, and the transmission rate of which can be up to 54 Mbps as well.
Although WLAN involves various kinds of wireless access techniques, most WLAN techniques utilize IP data packets for data transmission. The specific WLAN access technique adopted by a wireless IP network is usually transparent to the upper IP level. Such a wireless IP network is usually configured with Access Points (AP) for implementing wireless access of a WLAN UE, and with controlling and connecting devices for implementing IP data transmission.
Along with the appearance and development of WLAN, the inter-working of WLAN with various wireless mobile communication networks, such as GSM, CDMA, WCDMA, TD-SCDMA, and CDMA2000 has become the focus of research. This interworking network of WLAN and wireless mobile communication networks can also be called interworking-WLAN (I-WLAN). The invention is applied to, but not limited to I-WLAN. In accordance with the 3GPP (3rd Generation Partner Project) standards, a WLAN UE is not only able to connect with Internet and Intranet via the access network of WLAN, but also able to connect with the home network and the visited network of a 3GPP system via the WLAN Access Network. To be specific, when accessing locally, the WLAN UE is able to connect to the 3GPP Home Network via the WLAN Access Network, as shown in FIG. 2; when in case of roaming, the WLAN UE is able to connect to the Visited Network of the 3GPP system via the WLAN Access Network. And as some entities of the 3GPP Visited Network are connected with some corresponding entities of the 3GPP Home Network, for instance, the 3GPP Authentication, Authorization and Accounting (AAA) Proxy in the 3GPP Visited Network is connected with the 3GPP AAA Server in the 3GPP Home Network, the WLAN Access Gate (WAG) in the 3GPP Visited Network is connected with the Packet Data Gateway (PDG) in the 3GPP Home Network, and etc., as shown in FIG. 1. Wherein, FIG. 1 and FIG. 2 respectively illustrate the architecture of an inter-working network of a WLAN system and a 3GPP system under roaming and non-roaming circumstances.
As shown in FIG. 1 and FIG. 2, a 3GPP system primarily comprises Home Subscriber Server (HSS)/Home Location Register (HLR), 3GPP AAA Server, 3GPP AAA Proxy, WAG, PDG, Charging Gateway (CGw)/Charging information Collecting Function (CCF) and Online Charging System (OCS). WLAN UEs, WLAN access network, and all the entities of the 3GPP system together construct a 3GPP-WLAN inter-working network, which can be used as a WLAN service system. In this service system, 3GPP AAA Server is in charge of the authentication, authorization, and accounting of a WLAN UE, collecting the charging information sent from the WLAN access network and sending the charging information to the charging system; the PDG is in charge of the transmission of the user's data from the WLAN Access Network to the 3GPP network or other packet switching networks; and the charging system is in charge of receiving and recording the user's charging information sent from the network, and the OCS takes charge of instructing the network to periodically send online charging information in accordance with the expenses of the online charged users, meanwhile collecting statistics and controlling the network.
In the case of non-roaming, when a WLAN UE desires to access the Internet/Intranet directly, the WLAN UE can access to the Internet/Intranet via the WLAN Access Network after an authentication process with an AAA server (AS) via the WLAN Access Network. If the WLAN UE desires to access the services of 3GPP PS domain as well, it should further request the services of Scenario 3 from the 3GPP Home Network, which comprises: the WLAN UE sends a Service Authorization Request of Scenario 3 to the AS of the 3GPP Home Network, and the AS performs authentication and authorization to the Service Authorization Request, if the authentication and authorization are successful, the AS sends an Access Permission Message to the WLAN UE and assigns a corresponding PGD for the WLAN UE. After establishing a tunnel with the assigned PDG, the WLAN UE can access 3GPP PS domain services. At the same time, CGw/CCF and OCS records accounting information according to the use of network by the WLAN UE. In case of roaming, if a WLAN UE desires to access the Internet/Intranet directly, the WLAN UE will make a request to the 3GPP Home Network via the 3GPP Visited Network for accessing the Internet/Intranet. If the WLAN UE desires to access 3GPP PS domain, services requesting a Scenario 3 services as well, the WLAN UE needs to initiate a Service Authentication procedure via the 3GPP Visited Network to 3GPP Home Network, and similarly, the procedure is also implemented between the WLAN UE and the AS of the 3GPP Home Network. After the authentication procedure succeeds, the AS assigns a corresponding Home PGD for the WLAN UE, and after a tunnel with the assigned PDG is established via the WAG of 3GPP access network, the WLAN UE can access 3GPP PS domain services.
In 3GPP-WLAN inter-working networks, if a WLAN UE connects with multiple 3GPP Visited Networks, which refer to a plurality of Mobile Communication Networks, there are two schemes, as shown in FIG. 3 and FIG. 4 respectively, for the WLAN UE selecting a proper Mobile Communication Network to access according to its own requirements. FIG. 3 represents a successful process illustrating the WLAN UE directly selecting a Mobile Communication Network to access, which comprises:
Step 301-303: After establishing a wireless connection between the WLAN UE and a WLAN Access Network, the network or the WLAN UE initiates an access authentication procedure, the WLAN Access Network sends a User Identity Request packet to the WLAN UE; and after receiving the request packet, the WLAN UE returns a User Identity Response packet carrying network selection information to the WLAN Access Network. Here, the network selection information refers to the information of the Mobile Communication Network connected with the WLAN network and also to be accessed by the current WLAN UE; the access authentication procedure between the WLAN Access Network and the WLAN UE is based on an Expandable Authentication Protocol (EAP) procedure. In general, the network selection information is carried in a User Identity Field defined by a Network Access Identity (NAI) format.
Step 304-306: After receiving the packet sent from the WLAN UE, the WLAN Access Network judges whether the network selection information in the packet belongs to the Mobile Communication Network currently connected with the WLAN, if yes, the WLAN Access Network determines a 3GPP AAA Agent or a 3GPP AAA Server of the Mobile Communication Network selected by the WLAN UE according to NAI, and then sends the user identity and an Access Authentication Request to the determined 3GPP AAA Agent or 3GPP AAA Server, making 3GPP AAA Agent or 3GPP AAA Server authenticate to the currently accessing WLAN UE; if the authentication is passed, the subsequent access procedure will be accomplished.
FIG. 4 represents a process illustrating a WLAN UE reselecting a Mobile Communication Network to access according to the sent network selection information when the first selection fails, which comprises:
Step 401-403: These steps are exactly the same as Step 301-303.
Step 404-405: After receiving the packet sent from the WLAN UE, the WLAN Access Network finds that the network selection information in the packet does not belong to the Mobile Communication Network currently connected with the WLAN Access Network, and then sends a network notification signaling containing the information of all the Mobile Communication Networks connected with it to the WLAN UE.
Step 406-407: On receiving the signaling, the WLAN UE reselects a Mobile Communication Network to access according to the information of the Mobile Communication Networks contained in the information signaling, and then sends a User Identity Response packet carrying the selection information of the newly selected network to the WLAN Access Network.
Step 408-409: These steps are exactly the same as Step 305-306.
It can be seen from above schemes, there has been a relative consummate flow for a WLAN UE to select an access network in 3GPP-WLAN inter-working networks, however, when a WLAN Access Network connects with a plurality of VPLMN at the same time, and after a certain WLAN UE has accessed one of these VPLMN networks through the WLAN Access Network, the WLAN UE may need to disconnect the VPLMN network it currently connects and reselect another VPLMN network connected with the WLAN Access Network due to different reasons, such as charge, range of access service and so on; or the current WLAN UE expects to access Service A through VPLMN1 and access Service B through VPLMN2 at the same time. No specific scheme is proposed at present to resolve the above problems.